RP Resonator 2.0 – Advanced Software for
Laser Resonator Design and Optimization
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Example Case 1: Ring Resonator
We consider a ring resonator with a bow-tie geometry, containing a laser crystal with variable focusing power. The script first defines some parameters and then the resonator setup:
; ----------------------
; Resonator parameters:
a:=10 cm
b:=8 cm
R1:=40 cm
R2:=R1
theta:=6 deg
d:=2*b*cos(2*theta)-a
l_cr:=5 mm { length of crystal }
n_cr:=1.82 { refractive index of crystal }
F_cr:=3 { focusing power of crystal }
; ----------------------
resonator: ring
* mirror (M1): R = R1
* air: d = (a-l_cr)/2, "(a-l_cr)/2"
* prism (Crystal): l = l_cr, d = 2 mm, theta = 0, alpha = 0, n = n_cr, n2 = F_cr/l_cr
* air: d = (a-l_cr)/2, "(a-l_cr)/2"
* mirror (M2): R = R2, theta = theta
* air: d = b, "b"
* mirror (M3): theta = -theta
* air: d = d, "d"
* mirror (M4)
resonator end
Note that the closing air space is added automatically. Also, the software automatically adjusts the incidence angles on mirrors M1 and M4 such that the beam path is closed.
First, we want to have the resonator setup shown graphically in order to check that everything has been defined correctly:
graph 1, size_px=(600, 180): draw resonator, "Resonator Setup", showfocus
The result:
Now we plot the beam radius vs. position:
graph 2: "Beam Radius vs. Position" x: 0, L_res/mm "z position (mm)", @x y: 0, 400 frame hx hy f: w(x*mm,lambda_ref)/um, "w(z) (µm)", color=blue, width=3 ShowLine(z):=line(z/mm, z/mm+i*w(z,lambda_ref)/um) ! ShowLine(zm[M1]) "M1", ((z:=zm[M1])/mm)l, (w(z,lambda_ref)/um+10)b ! ShowLine(zm[M2]) "M2", ((z:=zm[M2])/mm)c, (w(z,lambda_ref)/um+10)b ! ShowLine(z1[Crystal]) ! ShowLine(z2[Crystal]) "crystal", ((z:=zm[Crystal])/mm)c, (w(z,lambda_ref)/um+10)b ! ShowLine(zm[M3]) "M3", ((z:=zm[M3])/mm)c, (w(z,lambda_ref)/um+10)b ! ShowLine(zm[M4]) "M4", ((z:=zm[M4])/mm)c, (w(z,lambda_ref)/um+10)b "M1", ((z:=L_res)/mm)r, (w(z,lambda_ref)/um+10)b
Some additional lines of code draw vertical lines and text labels, indicating the positions of the optical elements. For convenience, the function ShowLine(z) has been defined.
Next, we plot the beam radius at the laser crystal as a function of the dioptric power of the crystal:
graph 3: "Variation of the Dioptric Power of the Crystal" x: -15, +10 "dioptric power of the crystal (1/m)", @x y: 0, 600 frame hx hy clip f: (F_cr:=x; Init(0); w(zm[Crystal],lambda_ref))/um, "w(z) (µm)", color=blue, width=3, init F_cr0:=F_cr, finish (F_cr:=F_cr0; Init(0))
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